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"In part 1 of our look at Linux PAM, we learned how to remove
the annoying failed-login delay, lock out users who have too many
failed login attempts and how to set a restrictive fallback
configuration. Today we'll look at Linux distribution differences,
dig into the module types, what order to put things in, and what
the different options mean. You should have part 1 handy so you can
refer to the examples.

"Red Hat is (in)famous for heavily customizing its Linux
releases. This gets confusing when howto authors assume that Red
Hat = Linux and don't bother to point out the Red Hat-specific
bits, or when you're reading the program author's documentation and
it makes no sense for Red Hat. When you're studying PAM there are
two items in particular that you'll see a lot of that belong to Red
Hat and its derivatives: the pam_stack.so module, and the
system_auth file..."